Storage device



Dec. 20, 1960 P. M. JAFFE 2,965,783

STORAGE DEVICE Filed Oct. 27, 1958 Fig. l

Utilization Circuit 5 2 Photo Uiilizalion 5 i S Multiplier Circuit I L I20 43 35 g/jdeo I no 80%rce 2 Utilization Circuit --'vv\4v\,{||

3 Video Signal INVENTOR Philip M. Joffe Fig. 3

ATTORNEY United States Patent fltice 2,965,783 Patented Dec. 20, 1960STORAGE DEVICE Philip M. Jaffe, Nutley, N.J., assignor to WestinghouseElectric Corporation, East Pittsburgh, Pa., a corporation ofPennsylvania Filed Oct. 27, 1958, Ser. No. 769,806

6 Claims. (Cl. 313-108) This invention relates to electron dischargetubes and more particularly to storage tubes in which a cathode-ray beamis utilized.

In several types of storage tubes, it is necessary to utilize a lowvelocity electron beam. In the low velocity beam type of device, theelectrons in the electron beam normally reach the target withessentially zero velocity. It is also required that the landingelectrons strike the target substantially normal to its surface. Lowenergy electrons are difficult to control and it is necessary to useelaborate and expensive deflection and focusing systems in order toinsure the proper landing of the electrons. One method of overcomingthese problems is described in a copending application Serial No.580,855, entitled Electron Discharge Device by R. J. Schneeberger, filedApril 26, 1956, and assigned to the same assignee as the presentinvention. This invention overcomes this problem by utilizing adifferent type of storage target which enables the use of high energyeasily controlled electrons.

Certain electroluminescent materials exhibit the property of enhancedluminous output when excited by an electron beam and simultaneouslyplaced within the influence of a time varying electric field. That is,when the electron beam is modulated by an electrical signal and causedto scan a raster over the electroluminescent material, While an electricfield is present across the electroluminescent material, the imageformed on the material, representative of the modulated signal, will bebrighter than an image produced by an electron beam without thesimultaneous application of an electric field. This phenomenon isdescribed in a copending application Serial No. 518,321 by E. F. G.Arnott and H. F. Ivey, entitled Cathode Ray Screen and Method, filedJune 27, 1955 and assigned to the same assignee now Patent 2,863,084,issued December 2, 1958.

It has been found that these materials will also store the informationapplied by the modulated electron beam when simultaneously placed withinthe influence of an electric field. The stored information, which may bein the form of a latent image, may be released by removing the electricfield and scanning the material with a beam of electrons of uniformintensity. The information is released in the form of a transient image.

It is an object of this invention to provide an improved storage tube.

It is another object to provide an improved storage tube which utilizesa high energy electron beam.

It is another object to provide an improved storage tube, the output ofwhich is amplified in relation to the input.

It is a further object to provide a method for storing and subsequentlyreleasing a luminous output due to electron excitation of a fluorescentscreen.

An additional object is to provide a method for storing and subsequentlyreleasing with an enhanced output the response due to electronexcitation of a fluorescent screen.

An auxiliary object is to provide an improved storage device in whichthe stored information may be applied by a series of writing steps.

These and other objects are effected by this invention as will beapparent from the following description taken in accordance with theaccompanying drawing throughout which like reference characters indicatelike parts, and in which:

Fig. l is a sectional view of one embodiment of a storage tube inaccordance with the teachings of this invention.

Fig. 2 is a sectional view of another embodiment of a storage tube inaccordance with the teachings of this invention; and

Fig. 3 is a sectional view of a third embodiment of ,a storage tube inaccordance with the teachings ofthis invention.

In Fig. 1 there is shown an envelope member 11 having a neck portion 13a flared portion 15 and a faceplate 24. A suitable type of electron gun12 is disposed within the neck portion 13 to generate a beam ofelectrons. The electron gun 12 comprises at least a cathode 14, acontrol electrode 16 and an anode 18. The cathode 14 is connected to oneterminal of a direct current supply 52 and the control electrode 16 isconnected to the source 26 of the video signal to be stored. Suitableelectrostatic or electromagnetic deflection means may be positionedwithin the region of the neck portion 13 for defleeting the electronbeam from the gun 12 in both a horizontal and vertical direction to scana raster. In the specific embodiment shown, the electron beam from thegun 12 is caused to scan a raster by deflection means 20 which may beany suitable type of deflection yoke as is well known in the art. 1

A screen structure is positioned in the flared portion 15 of theenvelope member 11 near the face plate 24. The screen contains a layerof electroluminescent material 17 sandwiched between electricallyconductive layers 19 and 21. The electroluminescent layer 17 may be ahomogeneous layer of electroluminescent material or a mixture ofelectroluminescent material and a light transmissive dielectric materialsuch as polyvinyl-chlorideacetate. Where a mixture is preferred, theelectroluminescent phosphor may be embedded in the dielectric material.Positioned adjacent to the electrically conductive layer 21 furthestremoved from the electron gun 12 is a support layer 23 of a materialwhich is transmissive to the radiation emitted by layer 17, such asglass. On the opposite surface of the support layer 23 an electricallyconductive layer 25 is disposed. Adjacent to the exposed surface ofconductive layer 25 is positioned a layer of photoconductive material27. The photoconductive material is provided with another electricallyconductive layer 29 on the opposite side thereof. The conductive layers19 and 21 between which is disposed .the electroluminescent material 17are connected across a source 31 of a time varying voltage. The layer ofphotoconductive material 27 is also provided with a source 22 of directcurrent which is connected across the layers 25 and 29. A utilizationcircuit 35 is connected in series with the source 22 to use theinformation stored by the tube in any number of ways that may bedesired.

Examples of the phosphors suitable for use in the electroluminescentlayer 17 are zinc sulfide, cadmium sul- 'fide or mixtures thereofactivated by manganese, manganese-silver or manganese-gold. A specificexample of the phosphor may be 7 mole parts zinc sulfide and 1 mole partcadmium sulfide activated by -4 X 10* mole manganese. This phosphor maybe prepared byballmilling the aforementioned ingredients and firing inan oxygen free atmosphere for about one hour at 1100- C, Other examplesof the composition of the phosphor and 3 the preparation thereof can befound in the abovementioned c-opending application by Arnott and Ivey.

The conducting layers may be fabricated of any suitable electricallyconductive materials which may be coated as a thin sheet and aretransmissive to electrons in the case of conductive layer 19 andtransmissive to radiation emitted by layer 17 in the case of conductivelayers 21 and 25. The conductive layer 19 closest to the electron gunmay be of aluminum which may be applied by well-known vacuum-metalizingtechniques onto one surface of the electroluminescent layer 17. Theconductive layers 21 and 25 on both surfaces of the support member 23may be of a wire mesh, a thin metallic layer which is transmissive toradiation from layer 17, or a. thin layer of tin oxide, such as soldunder the trademark NESA by Pittsburgh Plate Glass Company, Pittsburgh,Pa. Conductive layer 29 may be either a thin metallic layer or a layerof tin oxide. Other suitable thin conducting coatings such as oxides ofcadmium, indium, titanium or silicon may also be used. The layer ofphotoconductive material 27 may be of any suitable material such asantimony trisulfide, cadmium sulfide, antimony selenide, cadmiumselenide, antimony telluride or cadmium telluride. The thickness of thephotoconducting layer 27 may be approximately 0.0002 inch, for example,to prevent lateral conductivity within the layer 27. The photoconductivelayer 27 may also be deposited in the form of a mosiac by evaporatingthe photoconductive material through a masking member. When cadmiumsulfide is used as the photoconductive layer 27 it may be prepared asdescribed by R. E. Aitchison in the science periodical Nature, vol. 167,No. 4255, May 19, 1951, pages 812 and 813. To obtain the maximumamplification of the stored information the photoconductive materialshould have its peak response at approximately the same wavelength oflight emitted by the electroluminescent layer.

In the operation of the device, as shown in Fig. 1, the electron beamgenerated by the electron gun 12 is modulated by a time sequentialinformation bearing signal from a video signal source 26 which is anelectrical signal of the information to be stored on the fluorescentscreen 17. The video signal source 26 may be in the form of a radar ortelevision receiver. For purposes of simplicity, the beam generated bythe electron gun 12 during this phase of operation will be called thewriting beam. A suitable accelerating voltage on the order of 4000volts, for example, may be applied between the cathode 14 of theelectron gun 12 and the conductive layer 19 by means of a direct currentsource 52. When the writing beam is operating, a time varying electricfield on the order of 4,000 volts/ cm. is applied across theelectroluminescent layer 17. The intensification of the output ofelectroluminescent layer 17 appears to be independent of the frequencyof the time varying electric field. Therefore, it is preferable to use afrequency of 60 cycles per second but this is not a requirement sinceother frequencies may be used, if desired. As the writing beam scans theelectroluminescent layer 17, in a point by point manner, a spacedistributed energy pattern is formed on the electroluminescent layer 17in which the energy condition of different elemental portions isrepresentative of successive portions of the information bearing signal.This energy pattern is representative of the signal applied to modulatethe writing electron beam. The information is nowstored on theelectroluminescent layer 17. If it is desired to apply additionalinformation to the electroluminescent layer 17 the writing beam willagain be operated. The time sequential information bearing signal tobe-applied Will be utilized to modulate the electron beam while thetime-varying electric field is applied across the conductive layers 19and 21 on either side-of thev electroluminescent layer 17. By such aprocedure-the information stored can be-=built-upby a seriesofewritingoperations: It is:-also possibleto-"scan the electroluminescent layer 17with a uniform beam of electrons while a field is impressed across layer17 and thereby obtain a multiple number of copies while still retainingthe stored information on the electroluminescent layer 17. To releasethe information stored by the electroluminescent layer 17 the timevarying electric field is removed from across the electroluminescentlayer 17. After removal of the electric field, the electron gun 12 ismade to generate a beam of electrons having a uniform intensity. Thisbeam is scanned over the electroluminescent layer 17 in any desiredraster so that the beam impinges on layer 17 point by point. Fors'implicity this beam Will be called the reading beam. As the readingbeam scans the electroluminescent layer 17 in a point by point manner,it causes elemental areas of the electroluminescent layer 17 whichcontain stored information to fluoresce with a transient enhancedluminous output in a radiation pattern of the information stored by theelectroluminescent layer 17 due to the action of the writing beam. Thelight output from the elemental areas of the electroluminescent layer 17causes a reduction in the resistance of corresponding elemental areas ofthe photoconducting layer 27 thereby modifying the current flow from theDC. source 22 through the photoconducting layer 27, to the utilizationcircuit as an electrical time sequential signal which corresponds to theoriginal signal utilized to modulate the writing beam but which isamplified with respect to the original signal. The different timesequential portions of the signal are representative of the energy ofthe successively scanned elemental areas.

Fig. 2 is similar to Fig. 1 with the exception that a photomultipliertube 43 is utilized to convert the stored information into a pulsedelectrical signal. In this embodiment a conducting layer 21 such asdescribed above, may be applied to the internal surface of the faceportion 24 of the envelope member 11'. The electroluminescent layer 17is disposed adjacent to this conducting coating 21 and a secondconducting layer 19 is disposed on the opposite surface of theelectroluminescent layer 17. A photomultiplier tube 43 is positioned insuch a manner as to receive the luminous response of theelectroluminescent layer 17. It may be desired in some instances toprovide an optical means between the face portion 24 and thephotomultiplier tube 43 to focus the output of the electroluminescentlayer 17 unto the photomultiplier tube 43. Because of the amplificationof the signal due to the transient enhanced output of theelectroluminescent layer 17 and the amplification of the photomultipliertube 43, the original signal is greatly multiplied which results in agreatly amplified output signal.

The operation of the device shown in Fig. 2 is similar to that describedabove for Fig. l. The time sequential information bearing signal to bestored is used to modulate the writing electron beam which is operatedsirnultaneously with the time varying electric field applied across theelectroluminescent layer 17 As the modulated writing beam scans theelectroluminescent layer 17 in a point by point manner, a spacedistributed energy patternis formed on the electroluminescent layer 17in which which the energy condition of different elemental portions isrepresentative of successive portions'of the information bearing signal.When the space distributed energy pattern isto be released, the field isremoved from the electroluminescent layer 17 and the electron gun 12 isoperated to generate a uniform intensity electron beam (i.e readingbeam) which is caused by deflection means 20 to scan theelectroluminescent layer 17 in a point by point manner. As the readingbeam scans the electroluminescent layer 17, the energy stored by eachelemental area is released successively in the form of a luminousoutput. The photomultiplier will convert the luminous output into anamplified electrical signal representative of the timesequentialinformation bearing. signa1.- utilized to. modulate thewriting-electron beam.

Fig. 3 shows a third embodiment of this invention which utilizes avidicon type scanning means to derive the electrical signalrepresentative of the stored information. The entire structure may beenclosed within a single evacuated envelope 60, or an ordinary vidiconmay be disposed closely adjacent to the face portion 24 of the envelopemember 11 as shown in Fig. 2.

The structure of the device to the left of the support layer 23 as shownin Fig. 3 is identical with that shown in Fig. 2. Positioned adjacentthe opposite side of the support layer 23 is an'electrically conductinglayer 25. A photoconductive layer 27 is disposed adjacent the conductinglayer 25. The right side of Fig. 3, or the vidicon portion 62 isprovided with the necessary, well known components (not shown) needed toproduce a beam of electrons and deflection means 63 to control this beamso that it may be scanned across the photoconductive layer 27 in pointby point manner. The cathode of the elec tron gun 50 and theelectrically conductive layer 25 are connected through load resistor 67to a source of direct current 65. The cathode is at a potential of about30 volts negative with respect to conductive layer 25. As the electronbeam from the gun 50 scans the photoconductive layer 27, the surface ofthe photoconductive layer 27 nearest the gun is charged to cathodepotential leaving a potential difference across the photoconductivelayer 27 of about 30 volts.

The operation of the writing electron beam to store the information onthe electroluminescent layer 17 and the reading beam to release thestored information is similar to that described above for Figs. 1 and 2.The information is stored by utilizing a time sequential informationbearing signal to modulate the writing beam and causing the beam to scanthe electroluminescent layer 17 in a point by point manner while a timevarying voltage is applied across the electroluminescent layer 17. Theinformation is released from the electroluminescent layer 17 by scanningwith an electron beam of uniform intensity in a point by point mannerafter the removal of the time varying voltage.

In the device shown in Fig. 3, the reading beam may be, if desired, aflood of electrons. If a scanning type beam is utilized as the readingbeam, however, it may be desirable to have the electron beam of theelectron gun 50 of the vidicon portion 62 in synchronism with thereading beam. As the reading beam releases the stored information fromelemental areas of the electroluminescent layer 17 in the form of alight output the conductivity of an adjacent elemental area of thephotoconductive layer 27 is modified causing the charge deposited on thesurface thereof to leak through the photoconductive layer 27 at a ratedetermined by the intensity of the illumination to which this elementalarea is subjected. The charge deposited the next time thephotoconductive layer 27 is scanned will be sufficient to replace thoseelectrons that have been lost by the leakage since the last passage ofthe electron beam. The charge the electron gun 50 deposits varies withtime in accordance with the variations in the illumination of thesuccessive elemental areas of the photoconductive layer 27. The currentthrough the load resistor 67, and hence the output voltage, thereforereproduces the variations in the light intensity of the successiveportions of luminous output of the electroluminescent layer 17 in theform of a time sequential information bearing signal.

The structure of the vidicon and its operation are explained more fullyon pages 984 through 986- of Electronic and Radio Engineering, by F. E.Terman, Fourth edition published by McGraw-Hill Book Company,Incorporated, 1955.

It can readily be seen that the storage tube of this invention not onlyprovides a means of storing information for a predetermined period oftime but also provides a means for obtaining an amplified timesequential information bearing signal. This device also eliminates theneed for the utilization of a low velocity electron beam and thussimplifies the construction.

While the present invention has been shown in several forms, it will beobvious to those skilled in the art that it is not so limited but issusceptible of various changes and modifications without departing fromthe spirit and scope thereof.

I claim as my invention:

1. A storage tube for storing information for a predetermined period oftime and subsequently releasing said information comprising afluorescent screen including phosphor material which exhibits theproperty of display ing an enhanced luminous output upon thesimultaneous application of electrons and an electric field, means forgenerating a writing electron beam modulated with a time sequentialinformation bearing signal to be stored on said fluorescent screen in aspace distributed energy pattern, means for applying a time varyingelectric field across said fluorescent screen during the operation ofsaid writing electron beam, means for generating a reading electron beamof uniform intensity to scan said fluorescent screen, and photosensitivemeans positioned adjacent said fluorescent screen to derive a timesequential information bearing signal representative of said energypattern released in the form of a luminous response to said readingelectron beam.

2. A storage tube for storing information for a predetermined period oftime and subsequently releasing said information comprising afluorescent screen of a material which exhibits the property ofdisplaying an enhanced luminous output upon the simultaneous applicationof electrons and an electric field, means for generating a writingelectron beam modulated with a time sequential information bearingsignal to be stored on said fluorescent screen in a space distributedenergy pattern, means for applying an alternating electric field acrosssaid fluorescent screen during the operation of said writing electronbeam, means for generating a reading electron beam of uniform intensityto scan said fluorescent screen, and photosensitive means positionedadjacent said fluorescent screen to derive a time sequential informationbearing signal representative of said energy pattern released in theform of a luminous response to said reading electron beam, saidphotosensitive means being a photoconductive layer positioned closelyadjacent to said fluorescent screen.

3. A storage tube for storing information for a predetermined period oftime and subsequently releasing said information comprising afluorescent screen of a material which exhibits the property ofdisplaying an enhanced luminous output upon the simultaneous applicationof electrons and an electric field, means for generating a writingelectron beam modulated with a time sequential information bearingsignal to be stored on said fluorescent screen in a space distributedenergy pattern, means for applying an alternating electric field acrosssaid fluorescent screen during the operation of said writing electronbeam, means for generating a reading electron beam of uniform intensityto scan said fluorescent screen, and photosensive means positionedadjacent said fluorescent screen to derive a time sequential informationbearing signal representative of said energy pattern released in theform of a luminous response to said reading electron beam, saidphotosensitive means being a photomultiplier positioned to receive theluminous response of the fluorescent screen upon operation of saidreading electron beam.

4. A storage tube for storing information for a predetermined period oftime and subsequently releasing said information comprising afluorescent screen of a material which exhibits the property ofdisplaying an enhanced luminous output upon the simultaneous applicationof electrons and an electric field, means for generating a writingelectron beam modulated with a time sequential information bearingsignal to be stored on said fluorescent screen in a space distributedenergy pattern, means for applying an alternating electric field acrosssaid fluorescent screen during the operation of said writing .electronbeam, means for generating a reading electron beam of uniform intensityto scan said fluorescent screen, and photosensitive means positionedadjacent said fluorescent screen to derive a time sequential informationbearing signal representative of said energy pattern released in theform of a luminous response to said reading electron beam, saidphotosensive means including a layer of photoconductive materialdisposed adjacent said fluorescent screen and a source of electronspositioned so that electrons emitted by said source will charge theexposed surface of said photoconductive layer.

5. A storage tube for storing information for a predetermined period oftime and subsequently releasing said information comprising afluorescent screen, including a finely divided material exhibiting theproperty of information storage upon the simultaneous application of anelectron beam containing said information to be stored and a timevarying electric field, means for generating a writing electron beammodulated with a time sequential information bearing signal to be storedon said fluorescent screen in a space'distributed energy pattern, meansfor applying a time varying electric field across said fluorescentscreen during the operation of said Writing electron beam, means forgenerating a reading electron beam of uniform intensity to scan saidfluorescent screen, and

photosensitive means positioned adjacent said fluorescent screen toderive a time sequential information bearing signal representative ofsaid energy pattern released'by said reading electron beam.

6. A storage tube for storing information for a predetermined period oftime and subsequently releasing said information comprising afluorescent screen including phosphor material which exhibits theproperty of displaying an enhanced luminous output upon the simultaneousapplication of electrons and an electric field, means for generating aWriting electron beam modulated with a time sequential informationbearing signal to be stored on said fluorescent screen in a spacedistributed energy pattern, means for applying an electric field acrosssaid fluorescent screen during the operation of said writing electronbeam, means for generating a reading electron beam of uniform intensityto scan said fluorescent screen, and photosensitive means positionedadjacent said fluorescent screen to derive a time sequential informationbearing signal representative of said energy pattern released in theform of a luminous response to said reading electron beam.

References Cited in the file of this patent UNITED STATES PATENTS V

